We have continued to obtain information from patients with cancer relative to their regional lymph nodes (RLNs) in order to ascertain whether such nodes should be preserved in the host or removed with a primary tumor. During the past year investigations were directed toward elucidating mechanisms responsible for nodal variations within a patient. In one series of studies a correlation was made between 3HT uptake by RLNCs and the position of nodes in the axilla as well as between nodal histopathological discriminants and nodal location. Findings indicated that variations in 3HT by RLNCs was at least in part related to the position of nodes in the axilla in that uptake by cells from low axillary nodes was greater than that by cells from high nodes. Sinus histiocytosis was unrelated to nodal location. While more low nodes contained lymph follicles there was no correlation between 3HT uptake and pressure or absence of follicles. It is concluded that high axillary nodes are more closely related functionally to distant than to low axillary nodes. Because of the possibility that the variations between nodes might be related to a difference in nodal cell type, T and B lymphocytes populations in nodes were determined. Such findings were correlated with peripheral blood lymphocytes in the same patient as well as those with benign breast disease. In general, no outstanding differences were observed which could account for the nodal variations within patients, particularly as related to axillary location. A comparison between peripheral blood T and B lymphocytes was made between patients with benign and with malignant breast disease. No significant differences were observed, as was the case when T and B lymphocytes in blood of cancer patients was compared with those cells in their lymph nodes.